Adhesives have been used for a variety of marking, holding, protecting, sealing and masking purposes. Adhesive tapes generally comprise a backing, or substrate, and an adhesive. One type of adhesive, a pressure sensitive adhesive, is particularly useful for many applications. Pressure sensitive adhesives are well known to one of ordinary skill in the art to possess certain properties at room temperature including the following: (1) aggressive and permanent tack at room temperature, (2) adherence with no more than finger pressure, (3) sufficient ability to hold onto an adherend, and (4) sufficient cohesive strength to be removed cleanly from the adherend. Materials that have been found to function well as pressure sensitive adhesives are polymers designed and formulated to exhibit the requisite viscoelastic properties resulting in a desired balance of tack, peel adhesion, and shear strength. The most commonly used polymers for preparation of pressure sensitive adhesives are natural rubber, synthetic rubbers (e.g., styrene/butadiene copolymers (SBR) and styrene/isoprene/styrene (SIS) block copolymers), various (meth)acrylate (e.g., acrylate and methacrylate) copolymers and silicones. Each of these classes of materials has advantages and disadvantages.
One class of pressure sensitive adhesive polymeric materials are (meth)acrylate polymers. These polymers contain acrylate and/or methacrylate monomers and may also contain reinforcing monomers such as, for example, (meth)acrylic acid. Many patents and publications describe the preparation of these polymers and pressure sensitive adhesive articles made from them, including, for example, U.S. Pat. No. RE 24,906 (Ulrich) which concerns pressure sensitive adhesive copolymer of about 88-97 parts of acrylic acid ester of non-tertiary alcohol, the alkyl groups of which have an average of 4-12 carbon atoms in the alkyl group, and correspondingly about 12-3 parts by weight of at least one modifying copolymerizable monomer such as acrylic acid, itaconic acid or acrylamide. A tape coated with the copolymer exhibits excellent adhesion and holding power, and the adhesive coating experiences no observable deterioration even after the tape has been stored for a number of years. Such tapes are widely used for a variety of purposes.
Pressure sensitive adhesive tapes that are used in the manufacture of articles to protect or temporarily hold in place components of the article during processing are sometimes called processing tapes. Examples of processing tapes include, for example, wafer dicing tapes, where the dicing tape may also function as a die attach adhesive for dicing thinned wafers and subsequent die attach operations of the diced chips in semiconductor device fabrication. Another example of a processing tape is a masking tape, where the masking tape is applied to a surface to cover it and protect it from being painted, the paint is applied, and the masking tape is removed to give a surface with adjacent areas that are painted and unpainted. Typically the processing tape is not retained in the final article, but is removed following one or more processing steps. In some instances, processing tapes are subjected to extreme conditions such as high temperatures, high pressures, exposure to chemicals such as solvents, abrasives, etching materials, and the like and yet are expected to remain adhered during the processing steps without flowing, dripping or slipping and also to be removable after the processing steps are completed.